Digital Control Design for a Circulating Fluidized Bed Unit Using Gamma Transmission Measurements
Antônio J. Cruz F.o 1*, Carlos C. Dantas1, Hilário J. B. de Lima F.o 2, Emerson A. O. Lima3, Silvio B. Melo4, Enivaldo S. Barbosa4.
1 Universidade Federal de Pernambuco – DEN/UFPE, Recife, PE, Brazil. email@example.com,
2 Universidade Católica de Pernambuco – UNICAP, Recife, Pernambuco, Brasil. firstname.lastname@example.org
3 Universidade de Pernambuco – UPE, Recife - PE, Brasil. email@example.com
4 Universidade Federal de Pernambuco – CIN/UFPE, Recife, PE, Brazil. firstname.lastname@example.org
5 Universidade Federal de Campina Grande – UFCG , Campina Grande - PB, Brasil. email@example.com
*Corresponding author e-mail: firstname.lastname@example.org.
A digital control design of a circulating fluidized bed pilot cold unit is proposed using pressure and gamma transmission as process variables. The pilot unit is compound for a riser of 6.700 m high and 0.092 m in diameter. The volume fraction and velocity of the catalyst were obtained in test sections that have sources of americium (Am-241) and shielded detector, positioned axially at 0.650, 1.384 and 3.424 meters. The gamma intensity is monitored by an 241Am isotopic gamma source and Na(Tl) scintillation detector. Three test sections for pressure and gamma transmission measurements are installed along riser. Lead shielding for source and detector plus collimators keep the adequate gamma flux for axial and radial scan. To overcome the challenge of modelling the solid transport unit further approaches included multivariable control (MV) and predictive control models (MPC) [1, 2]. Gamma-ray transmission techniques, used for estimate the particle concentrate distribution in a FCC riser, are known in the literature [3, 4, 5]. Circulating two-dimensional flow of pressure air and FCC – Fluid Catalytic Cracking catalyst, requires automation control, to keep steady state operational conditions. The mathematical control model describes the system using transfer function. The process transfer function is obtained by emulation and a digital controller is projected and analyzed. Independent variables are pressure, air flow and gamma transmission measurements by which the fluid parameters are determined. Using closed-loop feedback System and built in Matlab functions the transfer function simulation was carried out based on pressure and gamma transmission as control variables. The system response under controller action is taken to evaluate the injection of solids in the riser, and gamma-ray transmission is used to measure to solid concentration.
Keywords: Gamma radiation, pressure and gamma intensity, process control, solid transport.
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